1. Field of the Invention
The present invention relates to an ink jet printing method and an ink jet printing system for presenting information having a predetermined density on a print medium using a printing agent.
2. Description of the Related Arts
As the information processing apparatuses, such as personal computers, have spread, print apparatuses have been rapidly developed and have become popular as image forming terminals. Of the various types of print apparatuses presently available, ink jet print apparatuses, which to print by ejecting ink through discharge orifices onto printing media such as paper, cloth, plastic sheets and OHP sheets, have extremely superior characteristics, e.g., low-noise, non-impact type printing systems are employed, printing can be performed at a high dot density and at a high speed, color printing can be easily coped with, and prices are low. Today, ink jet print apparatuses constitute the mainstream of the print apparatuses available for personal use.
Continuing, accelerated technological advances in inkjet printing have yielded improvements in image quality, increases in operating speeds and reductions in prices that, taken together, have contributed greatly to the extended use of personal print apparatuses, paralleling the use today of personal computers and digital cameras (including not only self-contained cameras but also integrated components, of apparatuses such as cellular phones, that function as cameras). However, because the print apparatuses are widely used, a personal user demand has arisen for apparatuses which have improved image quality capabilities, and as a consequence, a particularly recent demand has arisen for home printing systems that can easily print pictures having image qualities equivalent to those of silver halide photography.
When an image printed by an ink jet print apparatus is compared with one produced by so-called ordinary silver halide photography, the granularity is viewed as an appropriate problem. Recently, a variety of countermeasures to minimize the granularity have been proposed, and many print apparatuses that incorporate these countermeasures have also been provided. For example, one ink jet print apparatus comprises an ink system that not only has common cyan, magenta, yellow and black ink, but also light cyan and magenta, which have lower densities. With this ink system, when light cyan or magenta is employed in a low density area, the dotted appearance can be minimized. Furthermore, when common cyan and magenta are used for printing in high density areas, greater and smoother tones can be reproduced.
Another method is one whereby, in order to minimize the granularity, a design is provided that reduces each dot size landing on a printing medium. For this method, the technology has been developed for reducing the size of ink volume to be discharged from individual printing elements arranged in a print head. In this case, not only is the size of the ink droplets reduced, but also, an arrangement including a greater number of printing elements is arranged in a higher density, so that a high resolution image can be formed with no decrease in printing speed.
For a personal use ink jet print apparatus, in addition to the acquisition of a high quality image, one almost the equivalent of a photograph, as described above, the apparatus is often desired that can also output general documents, such as text and charts or tables. For such documents, the speed at which printing is performed is more important than the ability to provide an image quality equivalent to that of a silver halide photograph. Therefore, a plurality of printing modes are provided for a general purpose ink jet print apparatus, so that a desired mode can be selected, as needed, by a user (see, for example, Japanese Patent Application Laid-Open No. 1-281944(1989)).
However, not all technological developments provided for the improvement of image quality can harmoniously coexist with a need to reduce costs and with printing modes for which the focus is on high speed printing. For example, for an ink jet print apparatus, for which the amount of ink discharged (hereinafter referred to as the discharged volume) by a printing element cannot be changed, in order to minimize the granularity, all the ink droplets discharged through the individual printing elements in a print head are defined as small droplets, having a fixed volume. The dots printed using the determined discharge volume are arranged at a preferred dot density, so that a desired density can be obtained (see, for example, the specification of Japanese Patent No. 03184744). Therefore, as the discharged volume is reduced, the printing dot density required to obtain a desired print density is increased, and accordingly, the configuration means and the required data processing are fixed, to a degree, and are complicated. Therefore, in a mode in which high speed printing is expected, the printing performed must depend on the configuration means and the data processing method described above, if a desired density is to be obtained. As a result, it is difficult for an appropriate density to be provided at a satisfactory printing speed.